Tuesday, August 25, 2009

Michael C. Feathers: Seven Blind Alleys in Software Design

sackgasse3_web.jpg Michael Feathers (author of Working Effectively with Legacy Code) gave an interesting talk at the Norwegian Developer Conference:
Seven Blind Alleys in Software Design.

The video of the talk can be found on this page.

Here is a short transcript of the seven dead alleys he identified:

1. Programming in Pictures
  • This has been a pipe-dream for years and years in the software industry.
  • "Anybody remember MDA?" (note the notion of the past ;-)
  • Some complexity is irreducible.
  • Pictures are not necessary better than words!
  • Word language symbolism vs. letter language symbolism. Thats the options we have, regardless if visual or textual.
  • Where are the real systems?
  • Think about the edge-cases.

  • 2. Metaprogramming
  • A result from the notion that it is hard to change code.
  • The promise is that it is easier to change data that represents things in the code.
  • We have to remember that code is data anyway.
  • Flexiblity vs. Understandability
  • Complexity is not reduced with flexibility.
  • Its hard to figure out what's going on in production.


  • 3. The Ultimate Abstraction
  • It always just seems one step away.
  • Believing in perfection
  • People don't want to make compromises
  • Programmers are abstraction junkies
  • Striving for the grand unified theory
  • Indicator: attempt to unify one and many
  • Deadlines and budgets help

  • 4. The perfect taxonomy
  • Do not try to create it upfront. Let it evolve and hope that it eventually will become stable.
  • Do not generalize too early -> failed framework projects.
  • Abstractions just have to be good enough not perfect.
  • English is ambiguous, programming ought not to be.

  • 5. Modeling the real world
  • Software is really different, it is subject to tighter constraints than the real word
  • If we can borrow concepts from the domain for our code, then that is great, but we don't have to.
  • Behavior is key. We can't always find a metaphor. We don't have to be limited by the concepts in the domain. We can make stuff up.
  • Why would you want to model the real world, thats where the problems are!
  • Classical example: Liskov substitution princple (Square/Rectangle)

  • 6. Code generation
  • Accept: You are never going to be complete! Don't be ambitious!
  • Traps! Can be shaping the code in bad ways.
  • Effect: De-skilling development
  • Encodes advanced knowledge of the domain which is likely to be wrong - workarounds are inevitable and get even the norm the older the system gets
  • Cruft buckets - Places where developers are forced to put their code. No design freedom possibe! Complexity cannot be tackled!

  • 7. Natural Languages
  • Business people are never going to be able to program - even in plain english
  • Programming is always going to be more constrained than plain english is
  • English seems easier, it does read better, but you have to think like a programmer!


  • I can't say that I always agree, but this presentation really allows you to take a step back and reflect. Michael addresses a lot of current and reoccurring hypes, and lets us remeber that there is no silver bullet.

    8 comments:

    1. Highly interesting.
      Like you, I am not sure I agree with everything, but I agree with most of the points.

      Michael did an excellent job in mapping the false hopes of our industry.

      ReplyDelete
    2. "Comlexity cannot be tackled!"

      WTF?

      'Comlexity'?

      ReplyDelete
    3. Sharp observations. I think that a lot of these alleys aren't absolutely blind (i.e. useless) but are often myopic (misleading the software writer into ignoring the trade-offs of his/her favorite "alley" and producing unmanageable code).

      ReplyDelete
    4. @Art
      "Myopic" - Interesting analogy! Thanks!

      ReplyDelete
    5. Funny that after all these years, we never managed to reduce complexity. Attempts to bridge the real-world with software concepts are hindered by the law of 1, 0 and nothing in-between. Fuzzy computers to the rescue, maybe?

      ReplyDelete
    6. One line of code is worth a thousand flowcharts.....

      ReplyDelete
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    8. These are brilliant points! You are very clever coming up with this list.

      ReplyDelete

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